In cataract surgery the pupil of the eye must first be dilated so that the surgeon has access to the lens. In many cases, conventional pupil dilating drugs are ineffective for this purpose. For example, if the patient has been undergoing glaucoma treatments he or she may very well have been using a myotic drug. Prolonged use of such medication tends to make the pupil fibrotic and resistant to dilation. Accordingly, in such cases, the cataract surgeon must mechanically dilate the pupil prior to surgery.
Conventional techniques for mechanically dilating the pupil exhibit various disadvantages. Typically, known mechanical dilators employ an intricate construction and are often quite difficult for the surgeon to manipulate and set in place. For example, in one technique, four retractors are surgically implanted into the eye. Each retractor includes a hook that holds a corner of the pupil in such a way that a square opening is created. In addition to being time consuming, complicated and expensive, this technique requires that four incisions be made in the eyeball. Precise manipulation of the iris is also required.
In another known technique, a water absorbent ring is inserted into the pupil. As the ring absorbs liquid and expands, it conforms to the shape of the pupil and causes it to dilate. This ring is difficult to introduce into and remove from the pupil. Additionally, it needs to be precisely manipulated in the eye by the surgeon.